Dual magnification dimension gage



March 17, 1959 A. M. DEXTER, JR 2,877,643 DUAL MAGNIFIdATION DIMENSION GAGE Filed Feb. 5, 1957 32 o 40 F, I I2 I 2 f AIR SUPPLY IN V EN TOR.

ALBERT M. DEXTER JD..-

United States Patent O DUAL MAGNIFICATION DIMENSION GAGE Albert M. Dexter, Jr., Farmington, Conn., assignor to Pratt & Whitney Company, Incorporated, West Hartford, Conn., a corporation of Delaware Application February 5, 1957, Serial No. 638,291

4 Claims. (Cl. 73--37.9)

This invention relates to dimension gages of the fluid type having a single gage head or gaging position, and more specifically to a gage of this type having an extremely high magnification and preferably dual magnification.

In fluid gages, a slight amount of friction exists throughout the range of movement of any linkage operated indicator. This friction may, for example, be caused by the condition of the linkage bearings, segment pivots, pointer shaft bearings, etc. In the practical embodiment of precision dimension gages found in the art, friction has been reduced to the lowest possible level consistent with cost and durability.

The desirability of simultaneously obtaining low and high magnification readings of a dimension from a single gaging device is obvious. In the present instance any frictional efiects in the low magnification linkage are not in any manner carried over into the high magnification linkage. The present invention overcomes frictional difliculties by providing effective isolation between the low and high magnification fluid circuits and linkage respectively.

In certain instances a gage having but one extremely high magnification may be called for. It is therefore a primary object to provide an extremely high amplification in a pneumatic gage in which any adverse effect of friction is reduced to a minimum.

In its preferred form, the dimension gage according to this invention comprehends (when providing dual magnification) at least a pair of flexible members with means arranged to admit fluid under variable signal pressures simultaneously to both said flexible members to flex portions thereof. Separate means are provided to indicate the amount of flexing of these members, the said indicating means operating over separate scales having different magnifications respectively.

Accordingly, it is an object of this invention to provide a dimension gage of the fluid type having dual magnification obtained from separate fluid circuits which are mechanically isolated.

Another object of the invention is to provide a dimension gage of the type described which will enable low and high magnification readings to be simultaneously obtained from a single gage head.

And finally it is an object of the invention to provide a dimension gage of the fluid or pneumatic type having an extremely high magnification.

The novel features characteristic of the invention are set forth with particularity in the appended claims. The

invention itself, however, both as to its organization and.

method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description when read in connection with the accompanying drawing in which:

Figure 1 is a schematic diagram of one illustrative embodiment of a dual magnification dimension gage of the fluid type made in accordance with the invention;

Fig. 2 is a pictorial view showing the relation of the nozzle sensing member with reference to one of the flexible members; and

Fig. 3 is a perspective view showing the cooperating mechanism for actuating the needles or pointers of the fine and coarse indicating means.

Referring more in detail to the drawing, air or other non-corrosive fluid under pressure is supplied to regulators 10 and 12, and from the regulators to separate adjustable restrictions 14 and 16 respectively. A conduit 18 conveys fluid from restriction 14 to a gaging plug member 20. The work piece or object 22 to be gaged is fitted over the gage head member 20 in the usual manner as shown in Fig. 1. In addition conduit 24 connects the fluid from conduit 18 to a first chamber or reservoir 26.

After leaving the restriction 16, fluid from regulator 12 is conveyed to a sensing nozzle member 28, and to a second chamber or reservoir 30 by means of pipes 32 and 34 respectively as shown. The sensing member 28 is adjustable axially and angularly as indicated in Fig. 1 and retained in adjusted position by means of suitable clamping member 33 and an adjustable arm 35. By varying the adjustment of nozzle 28 toward or from the flexible member 36 and angularly along the arc of member 36, variations in pressure within conduit 32 for slight flexing movements of member 36 may be increased or decreased. Adjustments axially and angularly of this nozzle member 28, with the proper regulator pressure and restriction adjustment, will permit varying the magnification obtainable from member 36, as the flexing of member 40, presently to be referred to more in detail, will be greater than that of member 36 for equal dimension changes in any gaging operation.

The two Bourdon tubes 36 and 38 are adapted to communicate with chamber 26; similarly, a third Bourdon tube 40 is arranged to communicate with chamber 30. While the flexible members 36, 38, 40 here shown are Bourdon tubes for illustrative purposes, it is within the scope of the invention to utilize other flexible members such as bellows, diaphragms, etc., to which fluid under variable pressures may be admitted.

As best shown in Fig. 3, tube 40 may be a single tube of broad width, or it may comprise twin tubes mechanically strapped together, so that the tubes will necessarily move in unison. In any event, in the operation of the gage the flexible member 40 will be treated as a single tube, and it is so shown in the schematic view Fig. 1.

Referring more specifically to Fig. 3, the end of Bourdon tube 40 is connected by a strap 48 to gear segment 50, which latter member is adapted to rotate about: fixed pivot 52. Similarly, tube 38 is connected by a strap 42 to gear segment 44, which segment rotates in an arcuate path about fixed pivot 46. Tube 36 is not attached to any form of linkage or needle but is free to flex with variable pressures from conduit 24 and chamber 26. Flexing movements of tube 36 therefore will be without friction of any kind. These flexing movements of tube 36 are utilized to vary or modify the degree of opening between the end face of nozzle 28 and the surface of tube 36. The segments 44 and 50 engage coaxially mounted pinions 54 and 56 respectively. The pinion 54 is mounted at one end of central shaft 58 which carries at the other end coarse indicating pointer 60. Pinion 56 is mounted on a hollow shaft 62, the outer end of which carries fine indicating needle 64. As may be seen from a study of Fig. 3, the shafts are arranged concentrically so that each is free to rotate about their common axis without interferencefrom the other.

While in the illustrative embodiment shown in the drawing three Bourdon tubes are shown, it is within the scope of the invention to employ but two Bourdon tubes or other responsive flexible members. However, the arrangement shown in the drawing is preferable when dual magnifications are required.

In describing the operation of the dual magnification gage, we may assume that the respective magnifications are adjusted .so that one division on the upper or coarse indicating dial is equal to l (.0001"), and that one division of the lower or fine indicating dial is equal to 2x10 (.00002). That is, the magnification of one is five times greater than the other. We may assume also, for example, that the bore of a work piece 22. being gaged is .00006" undersize. The coarse indicating needle 60 therefore should be displaced from its central zero position, on the negative side of the dial over which pointer or needle 60 travels, a distance equal to (three-fifths) of one division. This is hardly discernable to the naked eye. urthermore, errors in exact position of this pointer due to friction in the movement as re ferred to earlier, although not in themselves large, may be very large relative to the actual displacement from zero. However, the fine indicating needle 64 is displaced from its central zero position on the negative side of its dial, a distance equal to three full divisions,

which may be easily observed by an operator. Inherent errors in this movement are therefore relatively small.

For other dimensions being gaged the flexible members 36 and 38 will be flexed variable amounts. Variable flexing movements of member 38 resulting from varia tions in the work piece being gaged will vary the position of pointer 60 in the usual manner. Variable flexing of member 36 widens or decreases the gap between the end face of nozzle 28 and the outer surface of member 36. This varies the pressure built up in conduits 32 and 34 and hence determines the pressure admitted to chamber 30. to flexible member 40. The variable flexing of member 40 through link 48 varies the position of needle or pointer 64 over its scale in the usual manner.

When only a very high magnification is required, the tube 38 or other flexible member for actuating the needle 60 (and parts attached thereto) may be dispensed with. Flexible member 36 will be variably flexed by pressure variations in chamber 26 and by varying the opening of nozzle '28 will produce variable pressure diflerences in member 40 which will actuate its needle 64 over the high magnification dial.

While certain specific embodiments have been shown and described, it will be understood that various modifications may be devised by those skilled in the art which willembody the principles found in the true spirit and scope of the invention which is defined in the appended claims.

From chamber 30 the fluid is admitted I claim as my invention:

1. A dimension gage of the fluid type having a single gage head, a pair of flexible members, means to admit fluid under variable gaging pressures to said members, a needle movable over a dial, linkage connecting said needle to one of said members, whereby flexing thereof actuates said needle over its dial, a nozzle opened and closed by varying degrees by flexing of said second flexible member, a fluid supply circuit to said nozzle, the pressure within which is varied by flexing of said second member, a third member flexed by variations of said nozzle circuit pressure, a second needle movable over a second dial, and linkage connecting said second needle to said third flexing member whereby flexing thereof moves said second needle over its dial.

2. A dimension gage of the fluid type having a single gage head, a flexible member, means to admit fluid under variable gaging pressures to said member, a nozzle mounted adjacent said flexible member and opened and closed by flexing of said member, a fluid supply circuit to said nozzle the pressure within which is varied by flexing of said member, means to admit said fluid under variable pressures to a second flexible member, linkage connected to said second flexible member and a needle connected to said linkage, whereby flexing of said latter member will actuate said needle over its dial.

3. A dimension gage of the fluid type having a single gage head for determining a dimensional parameter of a work piece, comprising first and second flexible memhers, means to admit signal fluid pressures to said first member, a nozzle means arranged in a fluid circuit and mounted adjacent said first member, the fluid pressure within said nozzle means being a function of the displacement of said nozzle means from the first flexible member, means to admit pressure from said nozzle to said second flexible member, and means to indicate the magnitude of the displacement of said second flexible member on a dial, whereby the dial indication is a highly magnified reading of the parameter being gaged.

4. A dimension gage according to claim 3 in which the nozzle member is adapted for displacement in polar co-ordinates relative to the center of said indicating means.

References Cited in the file of this patent UNITED STATES PATENTS 2,065,702 Hubbard Dec. 29, 1936 2,284,795 Belaef June 2, 1942 2,457,401 Rupley Dec. 28, 1948 2,492,656 Rupley Dec. 27, 1949 2,667,886 Brewster Feb. 2, 1954 2,696,730 Justice Dec. 14, 1954 

